The present invention relates to a safety device for an apparatus under gas or vapor pressure such as a vessel, in particular for use in road vehicles.
Regulations require that vessels under gas pressure should safely withstand expected loads during operation. Moreover, safety devices, such as flow rate limiters and safety devices to protect against excess pressure are required in case of fire. According to technical standards for pressure gases TRG 381, vessels under gas pressure should be equipped with a fuse-type safety device or equivalent safety device to prevent excess pressure in case of fire and thereby protect against rupturing of the vessel. Larger vessels require application of several such trigger units, to ensure a sufficient pressure relief.
The use of fuse-type safety devices suffers, however, shortcomings because the employed solders are fairly expensive and progressively deform plastically over time when subject to a continuous load. Thus, so-called creeping, leads to an alteration of the response characteristic of the safety device, so that the condition of the fuse-type safety device cannot be assessed from outside.